Tree style tabs enables vertical tabs, which are listed at the side of the window rather than the top.

It means you can still read tab titles when you have more than a dozen tabs open. Plus you can nest and rearrange your tabs to fit your work or study.

For some, like me, it's a game changer and I dislike using chrome now because it doesn't support vertical tabs.

Caveat: to disable top-of-window tabs you have to use a user chrome CSS file, so it's not just "install extension, enable checkbox" easy.